svoid test_CutListToBudget() {
  var cutter = new CutListToBudget<S>(l1 l);
  cutter.allowPartial((s, l) -> takeFirst(s, l));
  cutter.maxPrice(3);
  cutter.inputList(ll("aaaaa"));
  assertEqualsVerbose(ll("aaa"), cutter!);
  assertEqualsVerbose("aaaaa", cutter.fullLastElement());
  assertEqualsVerbose(3.0/5.0, cutter.lastElementKeptPercentage());
}